Micro-electronic circuits and other micro-scale devices are generally manufactured by the sequential deposition and patterning of multiple layers on a substrate or wafer, such as a silicon or other semiconductor material wafer. For some applications, a metal film, e.g., tungsten, is deposited on the substrate to form micro-electronic or other micro-scale components or to provide electrical interconnects.
For some layers, to achieve desired material properties, the substrate is typically put through an annealing process in which the substrate is quickly heated, usually to about 200-500° C. and more typically to about 300-400° C. The substrate may be held at these temperatures for a relatively short time, e.g., 60-300 seconds. The substrate is then rapidly cooled, with the entire process usually taking only a few minutes. Annealing may be used to change the material properties of the layers on the substrate. Annealing may also be used to activate dopants, drive dopants between films on the substrate, change film-to-film or film-to-substrate interfaces, densify deposited films, or to repair damage from ion implantation.
As feature sizes for microelectronic devices and interconnects become smaller, the allowable defect rate decreases substantially. Some defects result from contaminants embedded in one or more of the layers.